A new study published in the journal JAMA Ophthalmology suggests there is no association between age-related macular degeneration and dementia or Alzheimer's disease, opposing previous research that has indicated otherwise.
According to researchers from the University of Manchester in England, both diseases share environmental risk factors and disease processes, such as smoking, high blood pressure, high cholesterol and depositing of plaques in the brain. But they note that genetic risk factors for both diseases appear to be "distinct."
Previous studies have suggested a link between AMD and cognitive impairment, the researchers say, but they add that these associations have been unclear.
"Controversy has surrounded whether these two conditions may be associated or not. The main reason behind this study was to address this controversy," Tiarnan D. L. Keenan, of the University of Manchester and lead study author, told Medical News Today.
"This is important, as it provides insights into how the diseases come about, and whether treatments for one condition might protect against or worsen the other."
The investigators looked to see whether patients suffering from AMD were more likely to develop Alzheimer's disease in the years following, and whether those with Alzheimer's were likely to develop AMD.
They analyzed a group of 65,894 patients with AMD, using data from the English National Health Service (NHS). The researchers also looked at data of 168,092 people with dementia and around 7.7 million people who did not have either disease.
Dementia screening for AMD sufferers 'may not be needed'
The findings revealed that people who suffered from AMD were no more likely to receive treatment for Alzheimer's disease or dementia than people who did not have AMD.
Furthermore, patients with Alzheimer's disease or dementia were around 20 times less likely to undergo treatment for AMD.
Explaining the importance of these findings, Keenan told Medical News Today:
"This means that people with age-related macular degeneration are not at higher risk of Alzheimer's disease or dementia, so may not need to undergo special screening. It also provides important insights to researchers trying to find treatments for these conditions."
Findings 'could indicate poor access to AMD treatment'
However, Keenan noted that their findings could suggest that some people with dementia may be going blind through poor access to treatment for AMD.
"This is very worrying, as people with dementia and blindness may be extremely isolated," he added.
He said that people with dementia are potentially vulnerable to neglect of other medical problems.
"In this case, dementia may mask visual loss and lead to inaction," he said. "Any suspicion of visual loss should prompt a full eye examination. Doctors also have their part to play. We need to identify potential barriers to care for these vulnerable individuals, and make our services and treatments more user-friendly."
Keenan said that future research will look into whether patients with dementia are developing AMD as a result of poor access to opthalmic care, and if so, this could potentially relate to other eye diseases, such as cataracts and glaucoma.
Medical News Today recently reported on a study detailing a new cognitive model that could detect early-stage dementia.